Adaptive transmission and receiving method and device in wireless communication system with multiple antennas

ABSTRACT

Disclosed is an adaptive transmit and receive method and device in a multiple-antenna wireless communication system. A transmit mode comprises different main transmit modes each of which includes one or both of a sub-transmit mode based on STBC and a sub-transmit mode based on SM. A receiver calculates an STBC performance parameter and a SM performance parameter, and a transmitter uses the parameters to determine a main transmit mode with maximum data rates and select a sub-transmit mode for minimizing power consumption. The transmitter channel-encodes, modulates and antenna-maps input data according to the selected transmit mode, and outputs results to the receiver. The receiver antenna/symbol-demodulates and channel-decodes the received data.

CROSS REFERENCE TO RELATED APPLICATION

[0001] This application claims priority to and the benefit of KoreaPatent Application No. 2003-20464 filed on Apr. 1, 2003 in the KoreanIntellectual Property Office, the content of which is incorporatedherein by reference.

BACKGROUND OF THE INVENTION

[0002] (a) Field of the Invention

[0003] The present invention relates to a wireless communication systemwith multiple antennas. More specifically, the present invention relatesto an adaptive transmission and receiving method and device in awireless communication system with multiple antennas.

[0004] (b) Description of the Related Art

[0005] The MIMO (multiple input multiple output) method, which is atransmission and receiving method using a plurality of antennas at atransmitter and a receiver, is one of the most noteworthy techniques inthe wireless/mobile communication systems because of its performanceimprovement possibilities in increasing spectral efficiencies anddiversity of transmission and reception.

[0006] One method for increasing data rates from among the transmissionand receiving methods with multiple antennas is an SM (spatialmultiplexing) method, in which a symbol sequence is divided into aplurality of sequences and transmitted to different transmit antennas.The symbols transmitted through the different antennas according to theSM method can be detected by using an OSIC (ordered successiveinterference canceller) receiver, a linear receiver based on ZF (zeroforcing) or the MMSE (minimum mean square error) criterion, or anoptimal ML (maximum likelihood) receiver.

[0007] Meanwhile, antenna diversity schemes are widely used to reduce amulti-path fading effect without increasing the data rates. Inparticular, the transmit diversity method by the Alamouti scheme in thecase of two transmit antennas is widely applied to 3^(rd) generationmobile communication systems and broadband radio-access systems, becausethe transmit diversity method provides simple configurations of thetransmitter and the receiver and enables acquisition of diversity oftransmit and receive channels. The Alamouti antenna transmit method isan orthogonal STBC (space time block code) for two transmit antennas.However, an orthogonal code exists only when two transmit antennas areprovided, and hence, pseudo orthogonal STBCs have been proposed forother numbers of transmit antennas. When such codes are applied in thefrequency domain as in the OFDM (orthogonal frequency divisionmultiplexing) transmission, they are called as SFBC (space frequencyblock code).

[0008] As described, since the SM method transmits a different symbolfor each transmit antenna, its performance is substantially changedaccording to features of elements of an MIMO channel, but since theperformance of an STBC method is determined not by each element of theMIMO channel but by the summation of the elements, the STBC method isless sensitive to the MIMO channel features, and hence, a desiredantenna transmit method can be differentiated according to the channelenvironments.

[0009] A prior art for improving performance such as capacity andquality in the multiple antenna system is disclosed in U.S. Pat. No.6,351,499 by Iospan which varies a number of transmit antennas for SMaccording to characteristics of the MIMO channel. However, since thenumber of the transmit antennas is varied, functions of a receiverbecome complicated, and the prior art does not exploit the advantages ofan STBC.

[0010] Together with this, an actively applied method for increasing thedata throughput in the current state is the adaptive modulation codingmethod which selects a modulation order and a code rate suitable fordesired performance according to an instantaneous state of fading andbackground noise intensity of a wireless channel, and transmits themvariably, thereby increasing the data throughput. The above-notedadaptive modulation coding method is applied to the HSDPA and the1xEV-DV which are evolved 3^(rd) generation mobile communicationsystems, and to the wireless LAN system and to the broadband radioaccess system, and it has been currently developed and commercialized.

[0011] However, selection references for channel state information and amodulation and coding method used by the conventional adaptivemodulation coding methods are difficult to directly apply to wirelesscommunication systems with multiple antennas that use spatialmultiplexing, performance of which is greatly varied according tocharacteristics of the MIMO channel.

SUMMARY OF THE INVENTION

[0012] It is an advantage of the present invention to provide anadaptive transmission and receiving method and device in a wirelesscommunication system with multiple antennas for adaptively modifyingcode rates, modulation methods, and antenna transmit methods accordingto channel environments.

[0013] In one aspect of the present invention, an adaptive transmitmethod of a transmitter in a wireless communication system with multipleantennas for transmitting data to a receiver with a plurality of receiveantennas from the transmitter with a plurality of transmit antennasthrough an MIMO channel, comprises: (a) determining a channel codingmethod, a modulation method, and an antenna transmit method so as tosupport different data rates according to a characteristic of the MIMOchannel, wherein the channel coding method, the modulation method, andthe antenna transmit method are classified according to a main transmitmode for supporting different data rates, and the main transmit modeincludes either or both of a sub-transmit mode based on the STBC and asub-transmit mode based on the SM; (b) encoding input data according tothe determined main transmit mode; (c) modulating the data encoded in(b) according to the determined sub-transmit mode, mapping them tomodulation symbols, and outputting results; and (d) mapping the datamodulated in (c) to symbol vectors to be transmitted through eachtransmit antenna according to the determined sub-transmit mode, andoutputting results.

[0014] The characteristic of the MIMO channel is indicated by an antennatransmit performance parameter produced and fed back by the receiver.

[0015] The (a) comprises: determining a main transmit mode that providesthe highest data rates from among the transmit modes (which includes themain transmit mode and the sub-transmit mode) that satisfy theperformance required according to the characteristic of the MIMOchannel, and determining a sub-transmit mode for reducing a transmitpower from the determined main transmit mode.

[0016] The (d) comprises: performing antenna mapping based on STBC whenperforming symbol mapping having a first symbol constellation on thesame main transmit mode in (c), and (d) comprises: performing antennamapping based on SM when performing symbol mapping having a secondsymbol constellation on the same main transmit mode in (c).

[0017] The (a) comprises: (i) comparing an STBC performance parameterwhich is one of parameters for showing the characteristic of the MIMOchannel with a previously stored STBC threshold value to select one ofthe main transmit modes having a sub-transmit mode based on the STBC ;(ii) comparing an SM performance parameter which is one of parametersfor showing the characteristic of the MIMO channel with a previouslystored SM threshold value to select one of the main transmit modeshaving a sub-transmit mode based on the SM; and (iii) comparing the maintransmit mode selected in (i) with the main transmit mode selected in(ii) to determine a final transmit. mode (which includes a main transmitmode and a sub-transmit mode.

[0018] The (i) comprises: selecting a main transmit mode which has aminimum positive number obtained by subtracting the STBC threshold valuefrom the STBC performance parameter, and (ii) comprises: selecting amain transmit mode which has a minimum positive number obtained bysubtracting the SM threshold value from the SM performance parameter.

[0019] The main transmit mode has indices in the ascending order of datarates, and (iii) comprises: determining whether the main transmit modeselected in (i) is greater than the main transmit mode selected in (ii);determining the main transmit mode selected in (i) and a sub-transmitmode based on STBC of the selected main transmit mode as final transmitmodes (which include a main transmit mode and a sub-transmit mode), whenthe main transmit mode selected in (i) is greater than the main transmitmode selected in (ii); and determining the main transmit mode selectedin (i) and a sub-transmit mode based on STBC of the selected maintransmit mode as final transmit modes (which include a main transmitmode and a sub-transmit mode), when the main transmit mode selected in(i) is matched with the main transmit mode selected in (ii), and thevalue obtained by subtracting the STBC threshold value from the STBCperformance parameter is greater than the value obtained by subtractingthe SM threshold value from the SM performance parameter.

[0020] The adaptive transmit method comprises: determining the maintransmit mode selected in (ii) and a sub-transmit mode based on SM ofthe selected main transmit mode as final transmit modes (which include amain transmit mode and a sub-transmit mode), when the main transmit modeselected in (ii) is greater than the main transmit mode selected in (i);and determining the main transmit mode selected in (ii) and asub-transmit mode based on SM of the selected main transmit mode asfinal transmit modes (which include a main transmit mode and asub-transmit mode), when the main transmit mode selected in (i) ismatched with the main transmit mode selected in (ii), and the valueobtained by subtracting the SM threshold value from the SM performanceparameter is greater than the value obtained by subtracting the STBCthreshold value from the STBC performance parameter.

[0021] In another aspect of the present invention, an adaptive receivemethod of a receiver in a wireless communication system with multipleantennas for transmitting data to the receiver with a plurality ofreceive antennas from a transmitter with a plurality of transmitantennas through an MIMO channel, comprises: (a) extracting symbolinformation for each antenna from a signal received through the MIMOchannel according to a channel coding method, a modulation method, andan antenna transmit method determined by the transmitter so as tosupport different data rates according to a characteristic of the MIMOchannel, wherein the channel coding method, the modulation method, andthe antenna transmit method are classified according to a main transmitmode for supporting different data rates, and the main transmit modeincludes either or both of a sub-transmit mode based on the STBC and asub-transmit mode based on the SM; (b) performing channel decodingaccording to the extracted symbol information for each transmit antenna,and estimating transmitted data information; and (c) extracting aparameter used by the transmitter for determining the channel codingmethod, the modulation method, and the antenna transmit method by usingan MIMO channel response estimated from the signal received through theMIMO channel.

[0022] The (c) comprises: (i) calculating an STBC performance parameterwhich is one of parameters for showing characteristics of the MIMOchannel by using the estimated MIMO channel response; and (ii)calculating a SM performance parameter which is one of parameters forshowing the characteristics of the MIMO channel by using the estimatedMIMO channel response.

[0023] The (i) comprises: calculating a channel power sum by using theestimated MIMO channel response; and calculating the STBC performanceparameter by combining the calculated channel power sum with theestimated MIMO channel response.

[0024] The (i) comprises: calculating a linear equalization matrix byusing the estimated MIMO channel response; calculating a transmitantenna post-processing SNR by using the calculated linear equalizationmatrix; and calculating the SM performance parameter by using thecalculated transmit antenna post-processing SNR.

[0025] In still another aspect of the present invention, an adaptivetransmit device in a wireless communication system with multipleantennas for transmitting data to a receiver with a plurality of receiveantennas from a transmitter with a plurality of transmit antennasthrough an MIMO channel, comprises: an adaptive transmit controller fordetermining a channel coding method, a modulation method, and an antennatransmit method so as to support different data rates according to acharacteristic of the MIMO channel, wherein the channel encoding method,the modulation method, and the antenna transmit method are classifiedaccording to a main transmit mode for supporting different data rates,and the main transmit mode includes either or both of a sub-transmitmode based on the STBC and a sub-transmit mode based on the SM; achannel encoder for encoding data input according to the channelencoding method determined by the adaptive transmit controller, andoutputting results; a symbol mapper for modulating the data encoded bythe channel encoder according to the modulation method determined by theadaptive transmit controller, mapping them to modulation symbols, andoutputting results; and an antenna mapper for mapping the data modulatedby the symbol mapper to symbol vectors to be transmitted through eachtransmit antenna according to the antenna transmit method determined bythe adaptive transmit controller, and outputting results.

[0026] The symbol mapper comprises: a first symbol mapper for modulatingthe data output by the channel encoder to a first symbol constellation,and outputting results; and a second symbol mapper for modulating thedata output by the channel encoder to a second symbol constellation, andoutputting results,

[0027] the antenna mapper comprises: a first antenna mapper forantenna-mapping the data modulated by the first symbol mapper accordingto the STBC method; and a second antenna mapper for antenna-mapping thedata modulated by the second symbol mapper according to the SM method,and

[0028] the adaptive transmit device further comprises: a demultiplexerfor connecting the output of the channel encoder to one of the first andsecond symbol mappers according to the modulation method determined bythe adaptive transmit controller; and a multiplexer for selecting one ofthe outputs of the first and second antenna mappers according to theantenna transmit method determined by the adaptive transmit controller.

[0029] The adaptive transmit controller comprises: an STBC thresholdvalue lookup table for storing threshold values of STBC; an SM thresholdvalue lookup table for storing threshold values of SM; an STBC transmitmode selector for comparing an STBC performance parameter fed back fromthe receiver with a threshold value stored in the STBC threshold valuelookup table to select one of the main transmit modes; an SM transmitmode selector for comparing an SM performance parameter fed back fromthe receiver with a threshold value stored in the SM threshold valuelookup table to select one of the main transmit modes; and a comparatorfor comparing the main transmit mode selected by the STBC transmit modeselector with the main transmit mode selected by the SM transmit modeselector to determine final transmit modes (which include a maintransmit mode and a sub-transmit mode).

[0030] In still yet another aspect of the present invention, an adaptivereceive device in a wireless communication system with multiple antennasfor transmitting data to a receiver with a plurality of receive antennasfrom a transmitter with a plurality of transmit antennas through an MIMOchannel, comprises: an antenna/symbol demodulator for extracting symbolinformation for each antenna from a signal received through the MIMOchannel according to a channel coding method, a modulation method, andan antenna transmit method determined by the transmitter so as tosupport different data rates according to a characteristic of the MIMOchannel, wherein the channel coding method, the modulation method, andthe antenna transmit method are classified according to a main transmitmode for supporting different data rates, and the main transmit modeincludes either or both of a sub-transmit mode based on the STBC and asub-transmit mode based on the SM; a channel decoder for performingchannel decoding according to the symbol information for each transmitantenna extracted by the antenna/symbol demodulator, estimatingtransmitted data information, and outputting results; a channelestimator for estimating an MIMO channel response from a signal receivedthrough the MIMO channel; and an adaptive transmit parameter extractorfor extracting a parameter used by the transmitter for determining thechannel coding method, the modulation method, and the antenna transmitmethod by using the MIMO channel response estimated by the channelestimator.

[0031] The adaptive transmit parameter extractor comprises: an STBCperformance parameter calculator for calculating an STBC performanceparameter by using an MIMO channel response estimated by the channelestimator; and an SM performance parameter calculator for calculating anSM performance parameter by using the MIMO channel response estimated bythe channel estimator.

[0032] The STBC performance parameter calculator comprises: a channelpower sum calculator for calculating a channel power sum by using theMIMO channel response estimated by the channel estimator; and a combinerfor combining the channel power sum calculated by the channel power sumcalculator with the MIMO channel response estimated by the channelestimator to calculate the STBC performance parameter.

[0033] The SM performance parameter calculator comprises: a linearequalizer for calculating a linear equalization matrix by using the MIMOchannel response estimated by the channel estimator; an SMpost-processing SNR calculator for calculating a transmit antennapost-processing SNR by using the linear equalization matrix calculatedby the linear equalizer; and a representative calculator for calculatinga representative of the SM performance parameter by using the transmitantenna post-processing SNR calculated by the SM post-processing SNRcalculator.

[0034] The antenna/symbol demodulator performs orthogonal diversitycombination by using the MIMO channel response estimated by the channelestimator to detect transmit symbols when the antenna transmit methoddetermined by the transmitter is a space encoding method, and to detectthe transmit symbols by using one of the ML detection method, the OSICdetection method, the MMSE linear equalization method, and the ZF linearequalization to method when the antenna transmit method determined bythe transmitter is a SM method.

BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The accompanying drawings, which are incorporated in andconstitute a part of the specification, illustrate an embodiment of theinvention, and, together with the description, serve to explain theprinciples of the invention:

[0036]FIG. 1 shows a block diagram of an adaptive antenna transmit andreceive device for a wireless communication system with multipleantennas according to a preferred embodiment of the present invention;

[0037]FIG. 2 shows a detailed block diagram of a transmitter of theadaptive antenna transmit and receive device for a wirelesscommunication system with multiple antennas according to a preferredembodiment of the present invention;

[0038]FIG. 3 shows an exemplified transmit mode supported by thetransmitter of the adaptive antenna transmit and receive device for awireless communication system with multiple antennas according to apreferred embodiment of the present invention;

[0039]FIG. 4 shows a flowchart of a transmit mode selection method atthe transmitter of the adaptive antenna transmit and receive device fora wireless communication system with multiple antennas according to apreferred embodiment of the present invention;

[0040]FIG. 5 shows a detailed block diagram of an adaptive transmitparameter extractor at a receiver of the adaptive antenna transmit andreceive device for a wireless communication system with multipleantennas according to a preferred embodiment of the present invention;and

[0041]FIG. 6 shows a detailed block diagram of an adaptive transmitcontroller of the adaptive antenna transmit and receive device for awireless communication system with multiple antennas according to apreferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0042] In the following detailed description, only the preferredembodiment of the invention has been shown and described, simply by wayof illustration of the best mode contemplated by the inventor(s) ofcarrying out the invention. As will be realized, the invention iscapable of modification in various obvious respects, all withoutdeparting from the invention. Accordingly, the drawings and descriptionare to be regarded as illustrative in nature, and not restrictive.

[0043] An adaptive antenna transmit and receive device for a wirelesscommunication system with multiple antennas according to a preferredembodiment of the present invention will be described referring tofigures.

[0044]FIG. 1 shows a block diagram of an adaptive antenna transmit andreceive device for a wireless communication system with multipleantennas according to a preferred embodiment of the present invention.

[0045] As shown in FIG. 1, the adaptive antenna transmit and receivedevice transmits and receives data through M transmit antennas and Nreceive antennas, and comprises a transmitter 110 for coding andmodulating the data and transmitting processed data through an MIMOchannel 120, and a receiver 130 for demodulating and decoding the datareceived through the MIMO channel 120 to restore the original data.

[0046] The transmitter 110 comprises an adaptive transmit controller111, a channel encoder 112, a symbol mapper 113, an antenna mapper 114,and a transmit end 115.

[0047] First, the adaptive transmit controller 111 selects an encodingmethod of the channel encoder 112, a modulation method of the symbolmapper 113, and an antenna mapping method of the antenna mapper 114according to a transmit mode selected by a signal fed back by thereceiver 130.

[0048] The channel encoder 112 receives data b_(i) to be transmitted,and encodes the same according to an encoding method selected by theadaptive transmit controller 111.

[0049] The symbol mapper 113 modulates the data encoded by the channelencoder 112 using a modulation method (e.g., QAM and PSK) selected bythe adaptive transmit controller 111, maps them to modulation symbolss_(j), and outputs result data.

[0050] The antenna mapper 114 receives outputs s_(j) of the symbolmapper 113, maps the outputs s_(j) to a symbol vector x_(j)=(x_(j,l) . .. , x_(j,M))^(T) to be transmitted through each transmit antennaaccording to an antenna mapping method selected by the adaptive transmitcontroller 111, and outputs result data.

[0051] The transmit end 115 receives outputs x_(j)=(x_(j,l) . . . ,x_(j,M))^(T) of the antenna mapper 114, configures signals according toa multi-carrier transmission method such as OFDM, or a single carriertransmission method and a multiple access method, and transmits thesignals to the MIMO channel 120 that is an MIMO channel through the Mtransmit antennas.

[0052] Multiple-antenna transmit outputs at the transmit end 115 areprovided to the receiver 130 with N receive antennas through the MIMOchannel 120.

[0053] The receiver 130 comprises a receive end 131, an antenna/symboldemodulator 132, a channel decoder 133, a channel estimator 134, and anadaptive transmit parameter extractor 135.

[0054] First, the receive end 131 performs an inverse operation of theprocess of the transmitter 110 to extract signals r_(j)=(r_(j,l) . . . ,r_(j,N))^(T) received through each receive antenna, and outputs them.

[0055] The antenna/symbol demodulator 132 acquires symbol informationfor each transmit antenna from the signals r_(j)=(r_(j,l) . . . ,r_(j,N))^(T) output by the receive end 131 according to transmit modeinformation determined by the adaptive transmit controller 111.

[0056] The channel decoder 133 performs channel decoding according tothe symbol information for each transmit antenna acquired by theantenna/symbol demodulator 132 to outputs result data {circumflex over(b)}_(i) that are estimates of the transmitted data information b_(i).

[0057] The channel estimator 134 receives the signals r_(j)=(r_(j,1) . .. , r_(j,N))^(T) output by the receive end 131, and estimates an MIMOchannel response by using pilot symbols.

[0058] The antenna/symbol demodulator 132 performs orthogonal diversitycombination by using the MIMO channel response estimated by the channelestimator 134 to detect transmit symbols when the antenna mapping methodfrom among the transmit mode information determined by the adaptivetransmit controller 111 of the transmitter 110 is a space encodingmethod, and to detect the transmit symbols by using one of the MLdetection method, the OSIC detection method, the MMSE linearequalization method, and the ZF linear equalization method when theantenna mapping method is an SM method.

[0059] The adaptive transmit parameter extractor 135 finds parametersfor the adaptive transmit by using channel estimation results output bythe channel estimator 134, and transmits the parameters to thetransmitter 110.

[0060] As a first example, outputs by the antenna mapper 114 followingthe STBC (or SFBC if it is applied in the frequency domain) method aregiven in Equation 1, and outputs by the antenna mapper 114 following theSM method are given in Equation 2 when the number M of the transmitantenna is 2.

x _(j)=(s _(j) −s* _(j+1))^(T), for even j

(s _(j) s* _(j−1))^(T), for odd j  Equation 1

x _(j)=(s _(2j) s _(2j+1))^(T)  Equation 2

[0061]FIG. 2 shows a detailed block diagram of a transmitter of theadaptive antenna transmit and receive device for a wirelesscommunication system with multiple antennas according to a preferredembodiment of the present invention.

[0062] The transmit mode of the transmitter according to the preferredembodiment includes at least one main transmit mode for supporting otherdata rates, and the main transmit mode includes two maximum sub-transmitmodes sharing the same channel encoding method.

[0063] As shown in FIG. 2, the transmitter of the adaptive antennatransmit and receive device comprises an adaptive transmit controller2200 for determining information on the main transmit mode and thesub-transmit mode, and a transmit mode block 2100 for transmitting inputdata according to the data rate determined by the transmit mode (maintransmit mode and sub-transmit mode) information output by the adaptivetransmit controller 2200.

[0064] The transmit mode block 2100 comprises a channel encoder 2110 forencoding input data according to the channel code rate r_(I) determinedby the transmit mode information I output by the adaptive transmitcontroller 2200; a sub-transmit mode 0 block 2130 for performing symbolmapping and antenna mapping on the sub-transmit mode 0; a sub-transmitmode 1 block 2140 for performing symbol mapping and antenna mapping onthe sub-transmit mode 1; a demultiplexer 2120 for connecting the channelencoder 2110 to one of the two sub-transmit mode blocks 2130 and 2140according to sub-transmit mode information output by the adaptivetransmit controller 2200; and a multiplexer 2150 for selecting one ofthe outputs of the two sub-transmit mode blocks 2130 and 2140 accordingto the sub-transmit mode information output by the adaptive transmitcontroller 2200.

[0065] In this instance, the sub-transmit mode 0 block 2130 comprises asymbol mapper 2131 having a modulation constellation Q_(I) ^(M), and anantenna mapper 2132 for space block coding, and sub-transmit mode 1block 2140 comprises a symbol mapper 2141 having a modulationconstellation Q_(I), and an antenna mapper 2142 for SM.

[0066] The sub-transmit modes 0 and 1 at the above-configuredtransmitter support the same data rate r_(l)M log2(Q_(l)), and one ofthe two sub-transmit modes is selected according to a characteristic ofthe MIMO channel.

[0067] The conventional adaptive transmit method supports a singletransmit mode configured by a specific transmit antenna method for asingle data rate, and the preferred embodiment uses a sub-transmit modeof using a different transmit antenna method to a main transmit mode ofsupporting the same data rates so as to maximize the data rates byapplying an MIMO channel characteristic.

[0068] In the preferred embodiment, all of the main transmit modes havetwo sub-transmit modes, and for ease of realization, the case ofsupporting a single sub-transmit mode from among the two sub-transmitmodes is also allowed.

[0069]FIG. 3 shows an exemplified transmit mode supported by thetransmitter of the adaptive antenna transmit and receive device for awireless communication system with multiple antennas according to apreferred embodiment of the present invention.

[0070] As shown in FIG. 3, the transmit mode has six main transmit modesthat support different data rates when two transmit antennas areprovided.

[0071] The main transmit modes 310 for supporting different data ratesare numbered from 0 to 5, and there is at least one sub-transmit mode320 that supports the respective main transmit modes 310, and it isassumed that a maximum of two sub-transmit modes are provided below.

[0072] Sub-transmit modes that support a single main transmit mode usethe same channel code rates 330, but use a different modulation method340 and transmit method 350. Part of the channel code rates 330, themodulation methods 340, and the antenna transmit methods 350 configuringdifferent main transmit modes 310 may be the same, but correspondingdata rates and performance are different.

[0073]FIG. 4 shows a flowchart of a transmit mode selection method atthe transmitter of the adaptive antenna transmit and receive device fora wireless communication system with multiple antennas according to apreferred embodiment of the present invention.

[0074] As shown in FIG. 4, the transmitter selects a main transmit modethat provides the highest data rates and reduces a transmit power fromamong the main transmit modes that satisfy the required performanceaccording to the characteristic of the MIMO channel, and a sub-transmitmode, when the number of the transmit antennas is M and the number ofthe main transmit modes having indexes in the ascending order of thedata rates is L.

[0075] First, a main transmit mode I_(B) with the minimum differenceΔ_(B,l)=S_(B)−T_(B,l)(Δ_(B,l)>0) between STBC performance parametersS_(B) greater than a threshold value T_(B,l) of the STBC mode and thethreshold value T_(B,l) is found in the main transmit modes having thesub-transmit mode 0 in step S10.

[0076] Next, a main transmit mode I_(M) with the minimum differenceΔ_(M,l)=S_(M)−T_(M,l)(Δ_(M,l)>0) between SM performance parameters S_(M)greater than a threshold value T_(M,l) of the SM mode and the thresholdvalue T_(M,l) is found in the main transmit modes having thesub-transmit mode 1 in step S20. In this instance, the order of thesteps S10 and S20 can be exchanged or the steps S10 and S20 can beexecuted in parallel.

[0077] The steps S10 and S20 represent a process for finding the maintransmit modes I_(B) and I_(M) that support the maximum data rates forsatisfying the required performance for the respective two sub-transmitmodes in the main transmit modes supported by the respectivesub-transmit modes.

[0078] Next, it is determined whether the transmit modes I_(B) and I_(M)found through the steps S10 and S20 satisfy that I_(B)>I_(M) or satisfythat I=I_(B)=I_(M) and Δ_(B,l)>Δ_(M,l) in step S30.

[0079] If I_(B)>I_(M) or if I=I_(B)=I_(M) and Δ_(B,l)>Δ_(M,l) thesub-transmit mode 0 of the main transmit mode I_(B) is selected in stepS40, or else the sub-transmit mode 1 of the main transmit mode I_(M) isselected in step S50.

[0080] In the step S30, a main transmit mode for supporting high datarates from among the data rates supported according to sub-transmitmodes, that is, a value having a large main transmit mode index isinitially selected, and when the data rates respectively supported bythe sub-transmit modes are the same, a mode for requiring less transmitpower, that is, a sub-transmit mode for further decreasing the transmitpower, is selected.

[0081] When the number of the transmit antennas is M according to thepreferred embodiment, the STBC performance parameter S_(B) is given asEquation 3. $\begin{matrix}{S_{B} = {{10\quad {\log_{10}( {SNR}_{SBC} )}} = {10\quad {\log_{10}( {\frac{{H}^{2}}{M}\frac{E_{S}}{N_{0}}} )}}}} & {{Equation}\quad 3}\end{matrix}$

[0082] where${{H}^{2} = {\sum\limits_{p = 1}^{N}{\sum\limits_{q = 1}^{M}{h_{p,q}}^{2}}}},{H = \begin{bmatrix}h_{1,1} & h_{1,2} & \cdots & h_{1,M} \\h_{2,1} & h_{2,2} & \cdots & h_{2,M} \\\vdots & \vdots & ⋰ & \vdots \\h_{N,1} & h_{N,2} & \cdots & h_{N,M}\end{bmatrix}}$

[0083] is an MIMO channel response,

[0084] E_(S) is a transmit symbol energy, and N₀ is the variance ofcomplex additive white noise.

[0085] Meanwhile, the SM performance parameter S_(M) can be given asEquation 4 for having the minimum value of the post-processing SNR as areference or Equation 5 for having the geometric mean of thepost-processing SNR as a reference.  S _(M)=min_(q)10 log₁₀(SNR_(SM,q))  Equation 4

[0086] $\begin{matrix}{S_{M} = {\frac{1}{M}{\sum\limits_{q = 1}^{M}{10\quad {\log_{10}( {SNR}_{{SM},q} )}}}}} & {{Equation}\quad 5}\end{matrix}$

[0087] From Equations 4 and 5, SNR_(SM,q) is a post-processing SNR ofthe symbol transmitted to the q-th transmit antenna, Equation 4 is foundbased on the fact that the performance before a channel decoding dependson the minimum SNR, and Equation 5 is for introducing a performanceimprovement caused by a well-performed symbol after the channeldecoding, and hence, usage of Equation 5 generates improved performanceafter channel decoding.

[0088] Equation 6 shows an SM post-processing SNR calculated based on alinear reception is processed, when the number of the transmit antennasis M. $\begin{matrix}{{SNR}_{{SM},q} = \frac{E_{S}g_{q}^{H}h_{q}}{{MN}_{0} + {E_{S}{\sum\limits_{j \neq q}^{\quad}{g_{q}^{H}h_{j}}}}}} & {{Equation}\quad 6}\end{matrix}$

[0089] where h_(q) is the q-th column vector of H, and g_(q) is the q-thcolumn vector of the linear equalization matrix G.

[0090] The linear equalization matrix G is differentiated according tothe linear equalization criterion, and it uses Equation 7 when using theZF criterion, and it uses Equation 8 when using the MMSE criterion.

G=(H ^(H) H)⁻¹ H ^(H)  Equation 7

[0091] $\begin{matrix}{G = {( {{H^{H}H} + {\frac{N_{0}}{{ME}_{S}}I_{M}}} )^{- 1}H^{H}}} & {{Equation}\quad 8}\end{matrix}$

[0092] After this process, the SNR can be used in any case when thereceiver uses any method for the antenna/symbol demodulator on the SM.The threshold value T_(M,l) and T_(l) for determining the transmit modeare modified according to the antenna/symbol demodulation method and theSM post-processing SNR calculation method.

[0093] Equation 9 shows the SNR after processing the SM methodcalculated based on the ZF criterion when the number of the transmitantennas is 2, and the number N of the receive antennas is greater than2. From Equation 9, Equation 4 can be given as Equation 10, and Equation5 can be given as Equation 11. $\begin{matrix}{{SNR}_{{SM},q} = {{\frac{1}{2( {H^{H}H} )_{qq}^{- 1}}\frac{E_{S}}{N_{0}}} = {{\alpha_{q}( {1 - \rho^{2}} )}{SNR}_{SBC}}}} & {{Equation}\quad 9}\end{matrix}$

[0094] where A_(qq) ⁻¹ is the (q,q)-th element of A⁻¹,$\alpha_{q} = \frac{{h_{q}}^{2}}{{H}^{2}}$

[0095] is a channel power ratio of the q-th transmit antenna,$\rho = \frac{{h_{1}^{H}h_{2}}}{{h_{1}}{h_{2}}}$

[0096] is a channel correlation between two transmit antennas, and ∥v∥is a norm of v.

S _(M)=10 log₁₀(α_(min)(1−ρ²))+S _(B)  Equation 10

[0097] where α_(min)=min_(q)α_(q).

S _(M)=10 log₁₀({square root over (α₁α₂)}(1−ρ²))+S _(B)  Equation 11

[0098] where α₁ and α₂ are channel power ratio for each transmitantenna, and ρ is a channel correlation of the transmit antenna.

[0099] Therefore, the channel power ratio for each channel transmitantenna can be calculated from the MIMO channel, and (S_(B)−S_(M)) canbe calculated from the channel correlation of the transmit antennainstead of directly calculating the SM performance parameter S_(M).

[0100]FIG. 5 shows a detailed block diagram of an adaptive transmitparameter extractor at the receiver of the adaptive antenna transmit andreceive device for a wireless communication system with multipleantennas according to a preferred embodiment of the present invention.

[0101] As shown in FIG. 5, the adaptive transmit parameter extractor 500comprises an S_(B) calculator 510 and an S_(M) calculator 520, andrespectively calculates the STBC performance parameter S_(B) and the SMperformance parameter S_(M) by using a channel response matrix estimateH and a receive SNR estimate E_(s)/N₀ input by the channel estimator.

[0102] The S_(B) calculator 510 comprises a channel power sum calculator511 and a combiner 512, and the channel power sum calculator 511calculates the channel power sum ∥H∥² by using a channel response matrixestimate input by the channel estimator.

[0103] The combiner 512 calculates the STBC performance parameter S_(B)following Equation 3 by combining the channel power sum calculated bythe channel power sum calculator 511 and the receive SNR estimateE_(S)/N₀ input by the channel estimator.

[0104] The S_(M) calculator 520 comprises a linear equalizer 521, an SMpost-processing SNR calculator 522, and a representative calculator 523.The linear equalizer 521 calculates the equalization matrix G shown asEquation 7 or 8 on the basis of the ZF or MMSE criterion.

[0105] The SM post-processing SNR calculator 522 calculates a transmitantenna post-processing SNR based on Equation 6 by using theequalization matrix G calculated by the linear equalizer 521.

[0106] The representative calculator 523 calculates a representative ofthe SM performance parameters S_(M) according to Equation 4 or 5 byusing the transmit antenna post-processing SNR calculated by the SMpost-processing SNR calculator 522.

[0107] The S_(B) calculated by the S_(B) calculator 510 and the S_(M)calculated by the S_(M) calculator 520 are quantized, or they areconverted to S_(B) and (S_(B)−S_(M)) and quantized, and fed back (501)to the transmitter so that the adaptive transmit controller of thetransmitter may use them to select a transmit mode.

[0108]FIG. 6 shows a detailed block diagram of an adaptive transmitcontroller 600 of the adaptive antenna transmit and receive device for awireless communication system with multiple antennas according to apreferred embodiment of the present invention.

[0109] As shown in FIG. 6, the adaptive transmit controller 600comprises a STBC transmit mode selector 610, a T_(B,I) lookup table 620,an SM transmit mode selector 630, a T_(M,I) lookup table 640, and acomparator 650.

[0110] The STBC transmit mode selector 610 compares the STBC performanceparameter S_(B) fed back (601) from the receiver with T_(B,I) values ofthe T_(B,I) lookup table 620 to calculate Δ_(B,l)=S_(B)−T_(B,l) as shownin the step S10 of FIG. 4, and outputs a main transmit mode value I_(B)which is a positive number and has the minimum value, and acorresponding Δ_(B,l).

[0111] The SM transmit mode selector 630 compares the SM performanceparameter S_(M) fed back (601) from the receiver with T_(M,I) values ofthe T_(M,I) lookup table 640 to calculate Δ_(M,l)=S_(M)−T_(M,l) as shownin the step S20 of FIG. 4, and outputs a main transmit mode value I_(M)which is a positive number and has the minimum value, and acorresponding Δ_(M,l).

[0112] The comparator 650 selects the sub-transmit mode 0 of the maintransmit mode I_(B) when l_(B)>l_(M), and selects the sub-transmit mode1 of the main transmit mode I_(M) when l_(B)<l_(M), as shown in the stepS30 of FIG. 4.

[0113] In addition, in the case that l=l_(B)=l_(M), the comparator 650selects the sub-transmit mode 0 of the main transmit mode I whenΔ_(B,l)>Δ_(M,l) and selects the sub-transmit mode 1 if not, therebyoutputting finally selected transmit mode and sub-transmit modeinformation.

[0114] According to the present invention, the main transmit mode fortransmitting specific data rates using the adaptive transmit method isconfigured with the transmit and receive method based on the SM antennatransmit method and the transmit and receive method based on the STBCantenna transmit method so as to adaptively select a desired methoddepending on the MIMO channel environment in the wireless communicationsystem with multiple antennas, thereby more effectively handling theMIMO channel environment to further increase the data rates in the giventransmit power, and reduce transmit power consumption in the given datarates.

[0115] While this invention has been described in connection with whatis presently considered to be the most practical and preferredembodiment, it is to be understood that the invention is not limited tothe disclosed embodiments, but, on the contrary, is intended to covervarious modifications and equivalent arrangements included within thespirit and scope of the appended claims.

What is claimed is:
 1. An adaptive transmit method of a transmitter in awireless communication system with multiple antennas for transmittingdata to a receiver with a plurality of receive antennas from thetransmitter with a plurality of transmit antennas through an MIMO(multiple input multiple output) channel, comprising: (a) determining achannel coding method, a modulation method, and an antenna transmitmethod so as to support different data rates according to acharacteristic of the MIMO channel, wherein the channel coding method,the modulation method, and the antenna transmit method are classifiedaccording to a main transmit mode for supporting different data rates,and the main transmit mode includes either or both of a sub-transmitmode based on the STBC (space time block code) and a sub-transmit modebased on the SM (spatial multiplexing); (b) encoding input dataaccording to the determined main transmit mode; (c) modulating the dataencoded in (b) according to the determined sub-transmit mode, mappingthem to modulation symbols, and outputting results; and (d) mapping thedata modulated in (c) to symbol vectors to be transmitted through eachtransmit antenna according to the determined sub-transmit mode, andoutputting results.
 2. The adaptive transmit method of claim 1, whereinthe characteristic of the MIMO channel is indicated by an antennatransmit performance parameter produced and fed back by the receiver. 3.The adaptive transmit method of claim 1, wherein (a) comprises:determining a main transmit mode that provides the highest data ratesfrom among the transmit modes (which include the main transmit mode andthe sub-transmit mode) that satisfy the performance required accordingto the characteristic of the MIMO channel, and determining asub-transmit mode for reducing a transmit power from the determined maintransmit mode.
 4. The adaptive transmit method of claim 1, wherein (d)comprises: performing antenna mapping based on STBC when performingsymbol mapping having a first symbol constellation on the same maintransmit mode in (c), and (d) comprises: performing antenna mappingbased on SM when performing symbol mapping having a second symbolconstellation on the same main transmit mode in (c).
 5. The adaptivetransmit method of claim 1, wherein (a) comprises: (i) comparing an STBCperformance parameter which is one of parameters for showing thecharacteristic of the MIMO channel with a previously stored STBCthreshold value to select one of the main transmit modes having asub-transmit mode based on the STBC; (ii) comparing an SM performanceparameter, which is one of parameters for showing the characteristic ofthe MIMO channel, with a previously stored SM threshold value to selectone of the main transmit modes having a sub-transmit mode based on theSM; and (iii) comparing the main transmit mode selected in (i) with themain transmit mode selected in (ii) to determine a final transmit mode(which includes a main transmit mode and a sub-transmit.
 6. The adaptivetransmit method of claim 5, wherein (i) comprises: selecting a maintransmit mode which has a minimum positive number obtained bysubtracting the STBC threshold value from the STBC performanceparameter, and (ii) comprises: selecting a main transmit mode which hasa minimum positive number obtained by subtracting the SM threshold valuefrom the SM performance parameter.
 7. The adaptive transmit method ofclaim 5, wherein the main transmit mode has indexes in the ascendingorder of data rates, and (iii) comprises: determining whether the maintransmit mode selected in (i) is greater than the main transmit modeselected in (ii); determining the main transmit mode selected in (i) anda sub-transmit mode based on STBC of the selected main transmit mode asfinal transmit modes (which include a main transmit mode and asub-transmit mode), when the main transmit mode selected in (i) isgreater than the main transmit mode selected in (ii); and determiningthe main transmit mode selected in (i) and a sub-transmit mode based onSTBC of the selected main transmit mode as final transmit modes (whichinclude a main transmit mode and a sub-transmit mode), when the maintransmit mode selected in (i) is matched with the main transmit modeselected in (ii), and the value obtained by subtracting the STBCthreshold value from the STBC performance parameter is greater than thevalue obtained by subtracting the SM threshold value from the SMperformance parameter.
 8. The adaptive transmit method of claim 7,comprising: determining the main transmit mode selected in (ii) and asub-transmit mode based on SM of the selected main transmit mode asfinal transmit modes (which include a main transmit mode and asub-transmit mode), when the main transmit mode selected in (ii) isgreater than the main transmit mode selected in (i); and determining themain transmit mode selected in (ii) and a sub-transmit mode based on SMof the selected main transmit mode as final transmit modes (whichinclude a main transmit mode and a sub-transmit mode), when the maintransmit mode selected in (i) is matched with the main transmit modeselected in (ii), and the value obtained by subtracting the SM thresholdvalue from the SM performance parameter is greater than the valueobtained by subtracting the STBC threshold value from the STBCperformance parameter.
 9. An adaptive receiving method of a receiver ina wireless communication system with multiple antennas for transmittingdata to the receiver with a plurality of receive antennas from atransmitter with a plurality of transmit antennas through an MIMO(multiple input multiple output) channel, comprising: (a) extractingsymbol information for each antenna from a signal received through theMIMO channel according to a channel coding method, a modulation method,and an antenna transmit method determined by the transmitter so as tosupport different data rates according to a characteristic of the MIMOchannel, wherein the channel coding method, the modulation method, andthe antenna transmit method are classified according to a main transmitmode for supporting different data rates, and the main transmit modeincludes either or both of a sub-transmit mode based on the STBC (spacetime block code) and a sub-transmit mode based on the SM (spatialmultiplexing); (b) performing channel decoding according to theextracted symbol information for each transmit antenna, and estimatingtransmitted data information; and (c) extracting a parameter used by thetransmitter for determining the channel coding method, the modulationmethod, and the antenna transmit method by using an MIMO channelresponse estimated from the signal received through the MIMO channel.10. The adaptive receive method of claim 9, wherein (c) comprises: (i)calculating an STBC performance parameter which is one of parameters forshowing characteristics of the MIMO channel by using the estimated MIMOchannel response; and (ii) calculating an SM performance parameter whichis one of parameters for showing the characteristics of the MIMO channelby using the estimated MIMO channel response.
 11. The adaptive receivemethod of claim 10, wherein (i) comprises: calculating a channel powersum by using the estimated MIMO channel response; and calculating theSTBC performance parameter by combining the calculated channel power sumwith the estimated MIMO channel response.
 12. The adaptive receivemethod of claim 11, wherein the STBC performance parameter SB satisfiesthe subsequent equation:$S_{B} = {{10\quad {\log_{10}( {SNR}_{SBC} )}} = {10\quad {\log_{10}( {\frac{{H}^{2}}{M}\frac{E_{S}}{N_{0}}} )}}}$

where${{H}^{2} = {\sum\limits_{p = 1}^{N}{\sum\limits_{q = 1}^{M}{h_{p,q}}^{2}}}},{H = \begin{bmatrix}h_{1,1} & h_{1,2} & \cdots & h_{1,M} \\h_{2,1} & h_{2,2} & \cdots & h_{2,M} \\\vdots & \vdots & ⋰ & \vdots \\h_{N,1} & h_{N,2} & \cdots & h_{N,M}\end{bmatrix}}$

is an MIMO channel response, E_(S) is a transmit symbol energy, and N₀is distribution of complex additive white noise.
 13. The adaptivereceive method of claim 10, wherein (i) comprises: calculating a linearequalization matrix by using the estimated MIMO channel response;calculating a transmit antenna post-processing SNR by using thecalculated linear equalization matrix; and calculating the SMperformance parameter by using the calculated transmit antennapost-processing SNR.
 14. The adaptive receive method of claim 13,wherein the linear equalization matrix G follows the equationG=(H^(H)H)⁻¹H^(H) in the case of a ZF (zero forcing) linear equalizationcriterion.
 15. The adaptive receive method of claim 13, wherein thelinear equalization matrix G follows the equation${{H}^{2} = {\sum\limits_{p = 1}^{N}{\sum\limits_{q = 1}^{M}{h_{p,q}}^{2}}}},{H = \begin{bmatrix}h_{1,1} & h_{1,2} & \cdots & h_{1,M} \\h_{2,1} & h_{2,2} & \cdots & h_{2,M} \\\vdots & \vdots & ⋰ & \vdots \\h_{N,1} & h_{N,2} & \cdots & h_{N,M}\end{bmatrix}}$

in the case of a MMSE (minimum mean square error) linear equalizationcriterion.
 16. The adaptive receive method of claim 14, wherein thetransmit antenna post-processing SNR follows the equation${SNR}_{{SM},q} = \frac{E_{S}g_{q}^{H}h_{q}}{{MN}_{0} + {E_{S}{\sum\limits_{j \neq q}{g_{q}^{H}h_{j}}}}}$

where SNR_(SM,q) is a post-processing SNR of the symbol transmitted tothe q-th transmit antenna, h_(q) is the q-th column vector of H, andg_(q) is the q-th column vector of the linear equalization matrix G. 17.The adaptive receive method of claim 16, wherein the SM performanceparameter S_(M) follows the equation S_(M)min_(q)10 log₁₀(SNR_(SM,q)) inthe case of setting the minimum value of the antenna post-processing SNRas a reference.
 18. The adaptive receive method of claim 16, wherein theSM performance parameter S_(M) follows the equation$S_{M} = {\frac{1}{M}{\sum\limits_{q = 1}^{M}{10\quad {\log_{10}( {SNR}_{{SM},q} )}}}}$

in the case of setting the geometric mean of the antenna post-processingSNR as a reference.
 19. The adaptive receive method of claim 17, whereinin the case that a number of the transmit antennas is 2, and a number ofthe receive antennas is greater than 3, when the transmit antennapost-processing SNR calculated based on the ZF linear equalizationcriterion is given as the equation${SNR}_{{SM},q} = {{\frac{1}{2( {H^{H}H} )_{qq}^{- 1}}\quad \frac{E_{S}}{N_{0}}} = {{\alpha_{q}( {1 - \rho^{2}} )}{SNR}_{SBC}}}$

where A_(qq) ⁻¹ is the (q,q)-th element of$A^{- 1},{\alpha_{q} = \frac{{h_{q}}^{2}}{{H}^{2}}}$

is a channel power ratio of the q-th transmit antenna,$\rho = \frac{{h_{1}^{H}h_{2}}}{{h_{1}}{h_{2}}}$

is a channel correlation between two transmit antennas, and ∥v∥ is anorm of v, the SM performance parameter S_(M) in the case of setting theminimum value of the antenna post-processing SNR as a reference followsthe equation S_(M)=10 log₁₀(α_(min)(1−ρ²))+S_(B) whereα_(min)=min_(q)α_(q).
 20. The adaptive receive method of claim 18,wherein in the case that a number of the transmit antennas is 2, and anumber of the receive antennas is greater than 3, when the transmitantenna post-processing SNR calculated based on the ZF linearequalization criterion is given as the equation${SNR}_{{SM},q} = {{\frac{1}{2( {H^{H}H} )_{qq}^{- 1}}\quad \frac{E_{S}}{N_{0}}} = {{\alpha_{q}( {1 - \rho^{2}} )}{SNR}_{SBC}}}$

where A_(qq) ⁻¹ is the (q,q)-th element of$A^{- 1},{\alpha_{q} = \frac{{h_{q}}^{2}}{{H}^{2}}}$

is a channel power ratio of the q-th transmit antenna,$\rho = \frac{{h_{1}^{H}h_{2}}}{{h_{1}}{h_{2}}}$

is a channel correlation between two transmit antennas, and ∥v∥ is anorm of v, the SM performance parameter S_(M) in the case of setting thegeometric mean of the antenna post-processing SNR as a reference followsthe equation S_(M)=10 log₁₀({square root over (α₁α₂)}(1−ρ²))+S_(B) whereα₁ and α₂ are channel power ratio for each transmit antenna, and ρ is achannel correlation of the transmit antenna.
 21. An adaptive transmitdevice in a wireless communication system with multiple antennas fortransmitting data to a receiver with a plurality of receive antennasfrom a transmitter with a plurality of transmit antennas through an MIMO(multiple input multiple output) channel, comprising: an adaptivetransmit controller for determining a channel coding method, amodulation method, and an antenna transmit method so as to supportdifferent data rates according to a characteristic of the MIMO channel,wherein the channel encoding method, the modulation method, and theantenna transmit method are classified according to a main transmit modefor supporting different data rates, and the main transmit mode includeseither or both of a sub-transmit mode based on the STBC (space timeblock code) and a sub-transmit mode based on the SM (spatialmultiplexing); a channel encoder for encoding data input according tothe channel encoding method determined by the adaptive transmitcontroller, and outputting results; a symbol mapper for modulating thedata encoded by the channel encoder according to the modulation methoddetermined by the adaptive transmit controller, mapping them tomodulation symbols, and outputting results; and an antenna mapper formapping the data modulated by the symbol mapper to symbol vectors to betransmitted through each transmit antenna according to the antennatransmit method determined by the adaptive transmit controller, andoutputting results.
 22. The adaptive transmit device of claim 21,wherein the symbol mapper comprises: a first symbol mapper formodulating the data output by the channel encoder to a first symbolconstellation, and outputting results; and a second symbol mapper formodulating the data output by the channel encoder to a second symbolconstellation, and outputting results, the antenna mapper comprises: afirst antenna mapper for antenna-mapping the data modulated by the firstsymbol mapper according to the STBC method; and a second antenna mapperfor antenna-mapping the data modulated by the second symbol mapperaccording to the SM method, and the adaptive transmit device furthercomprises: a demultiplexer for connecting the output of the channelencoder to one of the first and second symbol mappers according to themodulation method determined by the adaptive transmit controller; and amultiplexer for selecting one of the outputs of the first and secondantenna mappers according to the antenna transmit method determined bythe adaptive transmit controller.
 23. The adaptive transmit device ofclaim 21, wherein the adaptive transmit controller comprises: an STBCthreshold value lookup table for storing threshold values of STBC; an SMthreshold value lookup table for storing threshold values of SM; an STBCtransmit mode selector for comparing an STBC performance parameter fedback from the receiver with a threshold value stored in the STBCthreshold value lookup table to select one of the main transmit modes;an SM transmit mode selector for comparing an SM performance parameterfed back from the receiver with a threshold value stored in the SMthreshold value lookup table to select one of the main transmit modes;and a comparator for comparing the main transmit mode selected by theSTBC transmit mode selector with the main transmit mode selected by theSM transmit mode selector to determine final transmit modes (whichinclude a main transmit mode and a sub-transmit mode).
 24. An adaptivereceive device in a wireless communication system with multiple antennasfor transmitting data to a receiver with a plurality of receive antennasfrom a transmitter with a plurality of transmit antennas through an MIMO(multiple input multiple output) channel, comprising: an antenna/symboldemodulator for extracting symbol information for each antenna from asignal received through the MIMO channel according to a channel codingmethod, a modulation method, and an antenna transmit method determinedby the transmitter so as to support different data rates according to acharacteristic of the MIMO channel, wherein the channel coding method,the modulation method, and the antenna transmit method are classifiedaccording to a main transmit mode for supporting different data rates,and the main transmit mode includes either or both of a sub-transmitmode based on the STBC (space time block code) and a sub-transmit modebased on the SM (spatial multiplexing); a channel decoder for performingchannel decoding according to the symbol information for each transmitantenna extracted by the antenna/symbol demodulator, estimatingtransmitted data information, and outputting results; a channelestimator for estimating an MIMO channel response from a signal receivedthrough the MIMO channel; and an adaptive transmit parameter extractorfor extracting a parameter used by the transmitter for determining thechannel coding method, the modulation method, and the antenna transmitmethod by using the MIMO channel response estimated by the channelestimator.
 25. The adaptive receive device of claim 24, wherein theadaptive transmit parameter extractor comprises: an STBC performanceparameter calculator for calculating an STBC performance parameter byusing an MIMO channel response estimated by the channel estimator; andan SM performance parameter calculator for calculating an SM performanceparameter by using the MIMO channel response estimated by the channelestimator.
 26. The adaptive receive device of claim 25, wherein the STBCperformance parameter calculator comprises: a channel power sumcalculator for calculating a channel power sum by using the MIMO channelresponse estimated by the channel estimator; and a combiner forcombining the channel power sum calculated by the channel power sumcalculator with the MIMO channel response estimated by the channelestimator to calculate the STBC performance parameter.
 27. The adaptivereceive device of claim 25, wherein the SM performance parametercalculator comprises: a linear equalizer for calculating a linearequalization matrix by using the MIMO channel response estimated by thechannel estimator; an SM post-processing SNR calculator for calculatinga transmit antenna post-processing SNR by using the linear equalizationmatrix calculated by the linear equalizer; and a representativecalculator for calculating a representative of the SM performanceparameter by using the transmit antenna post-processing SNR calculatedby the SM post-processing SNR calculator.
 28. The adaptive receivedevice of claim 24, wherein the antenna/symbol demodulator performsorthogonal diversity combination by using the MIMO channel responseestimated by the channel estimator to detect transmit symbols when theantenna transmit method determined by the transmitter is a spaceencoding method, and to detect the transmit symbols by using one of theML (maximum likelihood) detection method, the OSIC (ordered successiveinterference canceller) detection method, the MMSE (minimum mean squareerror) linear equalization method, and the ZF (zero forcing equalizer)linear equalization method when the antenna transmit method determinedby the transmitter is an SM method.